In recent years, motor vehicles having an electric power train installed therein, for example, hybrid vehicles (hereinafter referred to as “HEV”) and plug-in hybrid vehicles (hereinafter referred to as “PHEV”) have been widespread. In each of those vehicles, a motor configured to propel the vehicle and an inverter and a step-up DC/DC converter, which are configured to drive the motor, are additionally installed in a configuration of a related-art gasoline engine vehicle. With this configuration, technological development for improving fuel efficiency and electricity efficiency is in progress.
As means for improving the fuel efficiency and the electricity efficiency, there is a method involving controlling an output voltage of the step-up DC/DC converter so as to minimize a total loss of a motor loss, an inverter loss, and a step-up DC/DC converter loss (for example, refer to Patent Literature 1).
Moreover, independently of the technological development for improving the fuel efficiency and the electricity efficiency, technological development for unifying platforms of the HEV/PHEV and the gasoline engine vehicle is in progress in order to decrease the vehicle prices of the HEV and the PHEV. In order to unify the platforms, it is indispensable to downsize the motor, the inverter, the step-up DC/DC converter, and the like, which are components added to the gasoline engine vehicle.